The present invention relates to a system for controlling a plurality of system devices mounted on a vehicle in an integrated manner. The system devices include an engine, a transmission and a brake device. More particularly, the present invention relates to an integrated vehicle control system appropriate for implementation of a quick response control according to the condition of the vehicle.
In order to keep up with the system""s complication accompanying an increasing number of system devices composing the vehicle, an integrated vehicle control system with a configuration, which allows control data to be exchanged among control devices provided individually to a plurality of system devices so that stable control can be executed for the vehicle as a whole.
In an integrated vehicle control system disclosed in U.S. Pat. No. 6,154,688 (JP-A-10-250417), for example, control devices for coping with control problems such as the engine""s driving and braking powers and control devices for controlling operating characteristics of the vehicle are positioned to form a hierarchical (layered) structure. In addition, a whole vehicle control unit for controlling these control devices in an integrated way is provided. Then, by providing required characteristics in the order from the highest level hierarchical layer to low level hierarchical layers, operations of system devices controlled by the control devices are determined and control optimum for the vehicle as a whole can be implemented.
By separating the control system of a vehicle into a plurality of subsystems as described above, it is possible to reduce the number of control system devices whose design needs to be changed, for example, when the specifications of the system are modified. Thus, the time it takes to change the design can be shortened. As an alternative, by maintaining mutual independence of the system devices, the individual system devices can be developed concurrently. As a result, required development time of a vehicle can be shortened as a whole.
With the conventional technology, however, a system device is no longer capable of operating with a quick response in dependence on the circumstances of system devices composing a vehicle in such a case that a system device mechanically reflecting an operation carried out by the driver in a direct manner is operated or a case that a failure or an abnormality occurs in the system device. A quick response operation for such cases cannot be taken due to the fact that control processing is carried out on the basis of a command from a control device placed on the highest level hierarchical layer.
When a driver changes a shift lever from the drive D range to the neutral N range in a running state of the vehicle, for example, it is not until transmission of an operation command of the shift lever to the highest level hierarchical layer that power transmission between the engine and the drive axle is turned off in accordance with the command coming from the highest level hierarchical layer. Thus, an operation cannot be taken quick in response to the operation carried out by the driver. In addition, in a vehicle equipped with a CVT (continuously variable transmission) an abnormality of an oil pressure mechanism for changing the transmission gear ratio may result in a circumstance in which the belt inadvertently slips. This is because, in this case, the highest level hierarchical layer issues a command to a lower level hierarchical layer in accordance with the abnormal condition so that a quick response operation can no longer be taken.
It is thus an object of the present invention to provide an integrated vehicle control system capable of responding to circumstances of system devices composing the vehicle.
An integrated control system for a vehicle according to the present invention comprises a plurality of system device control units for controlling a plurality of system devices in a vehicle; and a manager control unit for providing the system device control units with commands serving as operation directives of the system devices. At least a particular one of the system device control units attains a hierarchical layer secession determination process for determining whether a particular system device controlled by the particular system device control unit has entered a state requiring that a predetermined operation taking precedence of execution of an operation directive issued by the manager control unit to be carried out. If it is determined in the hierarchical layer secession process that the predetermined operation should be carried out, the particular system device control unit issues a command to the particular system device as an independent operation directive for driving the particular system device to carry out the predetermined operation independently of an operation directive issued by the manager control unit.